Distribution Of Light Source Research Articles

Cylindrical angular spectrum using Fourier coefficients of point light source and its application to fast hologram calculation.

We will introduce a new simple analytic formula of the Fourier coefficient of the 3D field distribution of a point light source to generate a cylindrical angular spectrum which captures the object wave in 360° in the 3D Fourier space. Conceptually, the cylindrical angular spectrum can be understood as a cylindrical version of the omnidirectional spectral approach of Sando et al. Our Fourier coefficient formula is based on an intuitive observation that a point light radiates uniformly in all directions. Our formula is defined over all frequency vectors lying on the entire sphere in the 3D Fourier space and is more natural and computationally more efficient for all around recording of the object wave than that of the previous omnidirectional spectral method. A generalized frequency-based occlusion culling method for an arbitrary complex object is also proposed to enhance the 3D quality of a hologram. As a practical application of the cylindrical angular spectrum, an interactive hologram example is presented together with implementation details.

A Spectral Database of Commonly Used Cine Lighting

In recent years, multiple methods have been published that describe how to estimate the spectral response of a camera system or object reflectance spectrum. These methods are becoming increasingly important for the color processing pipeline in movie productions. Knowing the spectral power distribution of light sources used in a movie production is essential for a spectral based approach to ensure a correct color reproduction in movie data creation. We present a thoroughly documented data set of spectral power distributions of typical film and TV lighting. The data set can be used to create more precise camera characterizations and help to develop spectral color processing pipelines. Furthermore, the spectral power distribution data set can be employed to detect and validate over-aged or damaged lighting, by comparing their spectra to our reference measurement.

Tunability of the circadian action of tetrachromatic solid-state light sources

An approach to the optimization of the spectral power distribution of solid-state light sources with the tunable non-image forming photobiological effect on the human circadian rhythm is proposed. For tetrachromatic clusters of model narrow-band (direct-emission) light-emitting diodes (LEDs), the limiting tunability of the circadian action factor (CAF), which is the ratio of the circadian efficacy to luminous efficacy of radiation, was established as a function of constraining color fidelity and luminous efficacy of radiation. For constant correlated color temperatures (CCTs), the CAF of the LED clusters can be tuned above and below that of the corresponding blackbody radiators, whereas for variable CCT, the clusters can have circadian tunability covering that of a temperature-tunable blackbody radiator.

Improvement of light uniformity by lighting arrangement for standardized crop production

In a commercialized, fully artificial plant factory, artificial luminaire is arranged in a unified way using a general illumination theory, an actual measurement, or an empirical methodology. However, with these methods, lightings are implemented without considering specific optical characteristics of lighting or material characteristics of each component that constructs a cultivation system, resulting in an amount of light that becomes irregular. The amount of lighting is closely related with the growth and quality of crops, and the deviation between points where cultivated crops are located causes quality difference in the produced crops, thus impairing the economic feasibility of a plant factory. In this regard, a simulation to figure out an optimum lighting layout was performed. Arrangements based on the spectrum distribution of light source and reflector materials were implemented to ascertain the distance between lighting and height of lighting and gather information in the pre-treatment process to improve the uniformity of light in the plant cultivation system. Improvement of around 15% in light uniformity is achieved compared with the existing system after the simulation is carried out. This result would reduce the deviation in crop growth to make uniform quality crop production possible.

Split Bregman迭代算法生物发光断层成像

In bioluminescence tomography applications, the spatial distribution of the interior bioluminescent light source is typically sparse in the imaging domain. Inspired by the compressive sensing recovery, a sparse reconstruction scheme based on l 1-norm regularization is presented for bioluminescence tomography. To obtain stable and fast reconstruction result, the Split Bregman iteration algorithm is employed to solve the l 1-norm regularized objective function. Numerical experiment results with a digital mouse model illustrate that the proposed method can accurately localize and quantify source distribution without either permissible source region constraint or multispectral measurements. The experimental results also show that the proposed algorithm has good robustness and ideal stability.

Experiments on Inverse Method to Illumination by Optimization Technique <i>IMIbyOPTIM</i> with Fixed Light Source Power

The present work reports an experimental procedure designed to validate a particular solution for the distribution of artificial light sources in the sealing of an enclosure obtained by the inverse method IMIbyOPTIM. An illumination design assuming the free placement of purely diffuse light sources aims to generate a uniform illumination field on a work plane. A reduced scale enclosure is built to validate the method effectiveness, by comparing the experimental results to an illuminance target. An equally non-optimized light source distribution is placed on the enclosure and measurements confirm the hypothesis of distortion of the illumination field, already predicted by simulations. After the optimization of the light sources distribution, the measured illumination field becomes closer to the dimensionless unitary target, with a standard deviation of less than 0.021. This particular experiment verifies IMIbyOPTIM predictions and allows continuing the validation process of the method for a broad variety of design combinations.

Recovering spectral data of metallic paints at various observation angles by digital camera

Purpose– In this article, a simple system will be presented to measure reflectance of metallic surfaces quickly and precisely based on goniospectrophotometric geometry. The paper aims to discuss these issues.Design/methodology/approach– This system works by capturing reflected light from different colored patches by digital camera and with the knowledge of spectral power distribution of light source and defined observer, reflection of each sample can be reproduced. By fixing the light source, the position of the detector would be eliminated to four angles of observation.Findings– This method can achieve acceptable reconstruction accuracy for metallic samples. This approach confirmed repeatability and practicality of the simple imaging acquisition to replace spectral reflectance measurement devices in different viewing angles.Originality/value– The reflectance of metallic samples has been measured at several angles such as 20°, 45°, 75° and 110° from specular reflection. A simple system was used to measure multi-angle reflectance of metallic surfaces by digital camera. By suggested system can be measured the reflectance without contact and limitation in the shape of surfaces. This method achieved acceptable reconstruction accuracy for metallic samples. This simple imaging acquisition is comparable with goniospectrophotometer for measuring multi-angle reflectance of metallic samples.

LED Lighting for Preferred Appearance of Facial Skin Color(<Special Issue>For the Further Spread of SSL and the Expansion of the Application Field)

Recently, LED light sources are becoming popular with the general lighting, such as offices, houses and shops. We can control easily the spectral distribution of the LED light sources, compared with the traditional light sources such as incandescent lamps, fluorescent lamps and so on. This article reports that we established spectral characteristics in order to develop LED light sources which improve the appearance of facial skin color, one of the important visual targets in lighting design. We conducted a subjective experiment with a novel index of the preference of facial skin color "PS" under various CCT (correlated color temperature) and D_<UV> (the distance from the blackbody curve for the color temperature) conditions. The results show that the best ranges of PS and D_<UV> differ depending on CCT. It is also found that the key spectral component for preferred appearance of facial skin color is in the range between 570 and 580 nm. Based on the result, we developed a series of new LED lighting fixture.

Night sky luminance under clear sky conditions: Theory vs. experiment

Sky glow is caused by both natural phenomena and factors of anthropogenic origin, and of the latter ground-based light sources are the most important contributors for they emit the spatially linked spectral radiant intensity distribution of artificial light sources, which are further modulated by local atmospheric optics and perceived as the diffuse light of a night sky. In other words, sky glow is closely related to a city's shape and pattern of luminaire distribution, in practical effect an almost arbitrary deployment of random orientation of heterogeneous electrical light sources. Thus the luminance gradation function measured in a suburban zone or near the edges of a city is linked to the City Pattern or vice versa.It is shown that clear sky luminance/radiance data recorded in an urban area can be used to retrieve the bulk luminous/radiant intensity distribution if some a-priori information on atmospheric aerosols is available. For instance, the single scattering albedo of aerosol particles is required under low turbidity conditions, as demonstrated on a targeted experiment in the city of Frýdek-Mistek. One of the main advantages of the retrieval method presented in this paper is that the single scattering approximation is satisfactorily accurate in characterizing the light field near the ground because the dominant contribution to the sky glow has originated from beams propagated along short optical paths.

Simulating the spatial luminance distribution of planar light sources by sampling of ray files

Ray files offer a very accurate description of the optical characteristics of a light source. This is essential whenever optical components are positioned in close proximity (near-field) of the light source in order to perform accurate ray tracing simulations. However, a ray file does not allow for a direct simulation of the spatial luminance distribution, i.e. luminance map, by off-the-shelf ray tracers. Simulating luminance maps of light sources or luminaires is especially important in general lighting in order to predict their general perception when viewed by the observer, and more specific, the perception of glare of luminaires having a non-uniform luminance distribution. To enable the simulation of luminance maps while maintaining the high accuracy offered by a ray file, a sampling method is presented. To validate the approach, near-field goniophotometer measurements of two planar light sources were performed. From these measurement data, ray files were extracted to which the sampling method was applied in order to obtain a set of surface sources. This approach was validated by comparing measured luminance images with simulated luminance images. A good agreement was found, validating the presented method.

Photometric characterisation of small sources with high dynamic range illuminance mapping

In this paper a system for obtaining the luminous intensity distribution of a small light source, based on high dynamic range imaging, is described. The system uses a dark room, a lambertian screen and a video-luminance-meter mounted on a workbench. The luminous intensity distribution of the light source is derived from the illuminance map on the screen by applying the photometric inverse law. The geometry of the system is presented and the measurements’ uncertainties are estimated. Finally, an application to a LED source is presented.

Extreme Spectral Power Distribution of Light Source and its Impact to Vision and Cameras Sensitivity

Extreme Spectral Power Distribution of Light Source and its Impact to Vision and Cameras Sensitivity

The Research of LED Lights Model Based on Road Lighting in Mesopic Vision

This paper analyzes the structural features of the human eye in the middle of the road lighting visual state of the visual request of road lighting in the Mesopic range of lighting, road lighting standards to build a white and green LED light source distribution model and defines the sharpness of the image according to the model function. In the Matlab7.1 environment, high pressure sodium yellow light LED white light and LED white and green background light, the model simulation analysis of the image clarity, results show that, in the Mesopic same brightness level state road lighting selection white and green the LED light source has better clarity and sensitivity.

A calibration‐free, one‐step method for quantitative photoacoustic tomography

Recently reported quantitative photoacoustic tomography (PAT) has significantly expanded the utilities of PAT because it allows for recovery of tissue optical absorption coefficient which directly correlates with tissue physiological information. However, the recovery of optical absorption coefficient by the existing quantitative PAT approaches strongly depends on the accuracy of absorbed energy density distribution, and on the knowledge of accurate strength and distribution of incident light source. The purpose of this study is to develop a new algorithm for the reconstruction of optical absorption coefficient that does not depend on these initial parameters. Here the authors propose a novel one-step reconstruction approach that can directly recover optical absorption coefficient from photoacoustic measurements along boundary domain. The authors validate the method using simulation and phantom experiments. The authors have demonstrated experimental evidence that it is possible to directly recover optical absorption coefficient maps using boundary photoacoustic measurements coupled with the photon diffusion equation in just one step. The authors found that the method described is able to quantitatively reconstruct absorbing objects with different sizes and optical contrast levels. Compared to the authors' previous two-step methods, the reconstruction results obtained here show that the one-step scheme can significantly improve the accuracy of absorption coefficient recovery.

Public Street Lights Increase House Infestation by the Chagas Disease Vector Triatoma dimidiata

Triatoma dimidiata is one of the primary vectors of Chagas disease. We previously documented the spatio-temporal infestation of houses by this species in the Yucatan peninsula, Mexico, and found that non-domiciliated triatomines were specifically attracted to houses. However, the factors mediating this attraction remained unclear. Artificial light has been known for a long time to attract many insect species, and therefore may contribute to the spread of different vector-borne diseases. Also, based on the collection of different species of triatomines with light traps, several authors have suggested that light might attract triatomines to houses, but the role of artificial light in house infestation has never been clearly demonstrated and quantified. Here we performed a spatial analysis of house infestation pattern by T. dimidiata in relation to the distribution of artificial light sources in three different villages from the Yucatan peninsula, Mexico. In all three villages, infested houses were significantly closer to public street light sources than non-infested houses (18.0±0.6 vs 22.6±0.4 m), and street lights rather than domestic lights were associated with house infestation. Accordingly, houses closer to a public street lights were 1.64 times more likely to be infested than houses further away (OR, CI95% 1.23–2.18). Behavioral experiments using a dual-choice chamber further confirmed that adult male and females were attracted to white light during their nocturnal activity. Attraction was also dependent on light color and decreased with increasing wavelength. While public lighting is usually associated with increased development, these data clearly show that it also directly contributes to house infestation by non-domiciliated T. dimidiata.

Three-dimensional imaging spectrometry by fully passive interferometry

We have developed a method to obtain a set of spectral components of three-dimensional (3D) images for a spatially incoherent, polychromatic light source distribution by a fully passive interferometric technique. The principle of the method is based on the measurement of a five-dimensional (5D) spatial coherence function and signal processing including the synthetic aperture technique and spectral decomposition. This paper gives a mathematical formulation illustrating the principle of the method, and we report an experimental demonstration in which the measured object is composed of two statistically uncorrelated point sources. The experimental results verify the applicability of our method to conventional spatially incoherent, polychromatic objects.

Comparison of permissible source region and multispectral data using efficient bioluminescence tomography method

As a novel molecular imaging technology, bioluminescence tomography (BLT) has become an important tool for biomedical research in recent years, which can perform a quantitative reconstruction of an internal light source distribution with the scattered and transmitted bioluminescent signals measured on the external surface of a small animal. However, BLT is severely ill-posed because of complex photon propagation in the biological tissue and limited boundary measured data with noise. Therefore, sufficient a priori knowledge should be fused for the uniqueness and stability of BLT solution. Permissible source region strategy and spectrally resolved measurements are two kinds of a priori knowledge commonly used in BLT reconstruction. This paper compares their performance with simulation and in vivo heterogeneous mouse experiments. In order to improve the efficiency of large-scale source restoration, this paper introduces an efficient iterative shrinkage thresholding method that not only has faster convergence rate but also has better reconstruction accuracy than the modified Newton-type optimization approach. Finally, a discussion of these two kinds of a priori knowledge is given based on the comparison results.

Research of Matching Character of Light Source in Integral Stereolithography System with Photo-Curable Resin

In order to choose right photo-curable resin for integral stereolithography (SL) system, researches have been carried out to find the matching of light source of integral SL System and the photo-curable resin. Spectrum distribution of light source is investigated with raster spectrum meter. The research result shows that main light power of the light source distributes in the span of 400-650nm, and there is few light power distributing in other span. Absorption spectrum of several photo-curable resin is measured with grating spectrometer, and measure results indicates that sample 1 (ad2230) has good absorption in the span of 0-650nm, and the average absorption ratio is above 80%. Other resins (ad2210, jd01, jd02) have only good UV absorption, the average absorption ratio is almost 100% particularly under 300nm, and the absorption band is under 350nm. As a result, ad2230 is the right photo-curable resin for integral SL system, and three-dimensional parts are fabricated by the integral SL System with the resin (ad2230). The research results lay a foundation for building objects with photo-curable resin by using integral SL System.

Simulation for light power distribution of 3D InGaN/GaN MQW LED with textured surface

In this paper, we introduce a full 3D simulation for light power distribution of an InGaN/GaN MQW LED with a textured surface. Device simulation was performed with the APSYS software to get power distribution of light sources inside the LED. Based on this, ray tracing simulation was carried out to get light power distribution outside the LED. During the process of ray tracing, the textured surface was treated as a special material interface whose reflectivity, transmittance and refraction angle are obtained with a Finite-Difference Time-Domain (FDTD) method instead of using the usual Fresnel formulas for normal material interfaces. By comparing the ray tracing results with and without the textured surface, we found that the textured surface yields a smoother transmitted power distribution and greatly improved power extraction efficiency, which are comparable to experiment. These effects may be further improved by optimizing the texture geometry.

Computer Simulation on Intensity Distribution of UV Irradiation System

The intensity distribution of a UV linear light source and a UV linear light with a parabolic cylinder reflector on work piece surface were simulated using OpenGL program based on VC++6.0. Physical models were established and relevant fundamental assumptions were given. The results of the simulation fitted the real situation quite well. It is feasible to adjust the parameters of UV-curing radiation system using the results of computer simulation.